PSA: Google Gmail is rate limiting again

[Bob Proulx]

Hello All Except for Gmail Users I guess,

This is just a PSA about administrivia stuff that happens behind the
scenes and usually is not visible...

Google has been twiddling their anti-spam controls again.  And it is
causing problems with delivery of NCLUG mailing list messages to Gmail
recipients.  If you are not using Gmail then you are receiving mailing
list messages normally.  However Google is rate limiting messages to
Gmail recipients.  Our Gmail subscribers are only seeing some of the
messages and not seeing all of them.  I see the issue when I look at
the mail queue.  Here is an example.  I'll format it to make it more
readable.

    BCCA4EA4      21692 Mon Jun 13 18:01:46  nclug-bounces at nclug.org
    (host alt1.gmail-smtp-in.l.google.com[173.194.77.27] said:
    421-4.7.28 [96.88.95.61      15] Our system has detected an unusual rate of
    421-4.7.28 unsolicited mail originating from your IP address. To protect our
    421-4.7.28 users from spam, mail sent from your IP address has been temporarily
    421-4.7.28 rate limited. Please visit
    421-4.7.28 https://support.google.com/mail/?p=UnsolicitedRateLimitError to
    421 4.7.28 review our Bulk Email Senders Guidelines. 72-20020a81124b000000b003138c843883si11952908yws.181 - gsmtp (in reply to end of DATA command))

And then it lists out all 50 of our Gmail address subscribers.  I
won't expose those addresses here.  But those recipicients don't get
the email.  Three messages from the recent threads are stuck in this
state right now from the past few days.  Hardly UBE Unsolicited Bulk
Email.  It's message discussion from our members.

I think the issue is because Google is seeing the same message to all
50 of those recipients all at once.  That's obviously most efficient.
Since it is the same message to all of them.  But Google then thinks
it must be UBE.  No one really knows what evil lurks in the heart of
Google since they don't make this information public.

This is a repeating issue.  And then after 5 days of being
undeliverable in the queue the message will be bounced back to Mailman
which will increment bounce counters for those recipients.  That has
been happening with previous messages.

The crazy thing is that not all messages get trapped this way.  For
example I correspond with people on Gmail *a lot* and therefore it
seems my content reputation survives through this limit.  I will
predict that this message from me will be passed through.  Useful
because I can make this PSA about Gmail not accepting mail.  Irony.
The opposite of wrinkly.

I am going to try some configuration changes which will hopefully make
Google happier with the mailing list.  Hopefully this won't break
things.  But if it does at least you know why I am trying these things.

Bob